Draw works

ABSTRACT

In the drawworks for lowering and withdrawing a load, in particular a drilling or a drilling plugging device, in particular for use on floating drilling platforms, which drawworks has at least one brake arrangement for braking and holding the load, an emergency brake device is provided for producing an additional braking force.

The invention relates to a drawworks for lowering and withdrawing aload.

Such drawworks serve to lower and withdraw a load, in particular adrilling device or a borehole plugging device, for example from afloating platform onto the sea bottom or into or onto a borehole. Theyhave a rotatably mounted winding drum, to which a flexible draw means isfastened, which is usually designed as steel cable and can be wound upor unwound by rotary drive of the winding drum.

At least one rotary drive device is provided for the rotary drive of thedrum. This rotary drive device regularly comprises an electric motor.However, it is likewise possible to use a hydraulic or pneumatic driveinstead of a direct-current motor.

To brake the winding drum during the lowering of the load and to holdthe load above the bottom, such drawworks have a brake device whichcomprises a mechanically acting brake arrangement. To relieve thismechanically acting brake arrangement, further brake arrangements whichdo not act mechanically, for example eddy-current brake arrangements,may also be provided.

In practice, the drawworks are adapted in their construction to themaximum hoisting capacity to be expected, which is determined by theintended use of the drawworks. Said hoisting capacity, by definition, isspecified for the first cable layer on the winding drum. For furtherwinding layers, i.e. during further winding-up of the cable onto thewinding drum, the maximum hoisting capacity decreases due to the largerlever associated therewith, under which the load acts on the windingdrum.

For safety, the cable is dimensioned in such a way that its breakingload corresponds to at least twice the hoisting load of the drawworks.The superstructures via which the cable is deflected—for example amast—are designed for 1.8 times the hoisting load. In order to avoid asituation, caused by actuation of the brake device, in which forces canbe exerted on the superstructures or the cable which are greater thanthe breaking load of these components, the brake device is conceived insuch a way that the maximum load to be held corresponds to 1.5 to 1.6times the hoisting load.

In the past, incidents have repeatedly occurred in which an unwindingoperation could not be stopped or could not be stopped in good time bymeans of the brake device. A possible cause for a series of suchincidents could have been that loads were held above the bottom close tothe maximum hoisting load with multiple cable layer on the winding drum,which has finally led to overloading of the brake device.

The object of the invention is therefore to improve the operationalsafety of such drawworks.

Owing to the fact that, according to the invention, an emergency brakedevice is provided for producing an additional braking force, the brakedevices used hitherto, which—as described above—offer protection againstoverloading of other components and ensure trouble-free operation in thevast majority of applications, can continue to be used. The additionalemergency brake device now enables an additional braking force to beapplied if required, i.e. if the braking power is momentarilyinadequate. Since the emergency brake devices are devices which areprovided in addition to the brake device, and the latter is not simplydimensioned to be larger, the emergency brake devices are only activatedwhen they are actually required. Braking of the winding drum istherefore even possible in the event of a total failure of the brakedevice.

In a first preferred embodiment of the drawworks according to theinvention, the brake arrangement has at least one brake shoe acting on arotary part and a device for applying a braking force to the at leastone brake shoe, the emergency brake arrangement being designed in such away that an additional device for optionally exerting an additionalbraking force on the rotary part is provided. If the braking power whichcan be achieved with the brake arrangement in normal operation is nolonger sufficient, additional braking power can be actively produced byactuating the additional device.

The device for applying a braking force to the at least one brake shoepreferably comprises a spring arrangement applying the braking force tothe at least one brake shoe. To control the braking force exerted on thebrake shoe, the device comprises an arrangement which acts in theopposite direction to the spring arrangement and is intended forcontrolling the braking force exerted on the brake shoe. This measureensures that, if the hydraulic device fails, the brake shoes are pressedagainst the brake disk with the maximum force, so that the maximumbraking power is produced.

The additional device is then preferably designed in such a way that itcomprises an arrangement for displacing the seat absorbing the reactionforces of the spring arrangement. When the additional device isactuated, the preloading of the spring arrangement is thereforeincreased, which leads to an increase in the braking force acting on theat least one brake shoe and thus to an increase in the braking power.

The additional device is preferably designed as a device which can beactuated hydraulically.

In a further preferred embodiment of the drawworks according to theinvention, the emergency brake arrangement comprises an additional brakedevice which can be engaged alternatively to the brake arrangement.

If the brake arrangement and emergency brake arrangement are designed insuch a way that in each case at least one hundred percent of the maximumbraking power required can be achieved with them, the emergency brakearrangement can completely replace the brake arrangement, so thatemergency operation of the drawworks is possible even in the event ofcomplete failure of the brake arrangement.

The construction of the emergency brake arrangement can at leastessentially correspond to that of the main brake arrangement.

If the drawworks comprises at least one gearbox coupled on the inputside to a drive motor and interacting on the output side with asummation gear, it is possible to arrange the emergency brakearrangement on the input side and/or on the output side of the gearbox.

The emergency brake arrangement can be engaged manually.

Especially preferred, however, is an embodiment in which a controldevice is provided which compares the respective braking-power setpointwith a parameter characteristic of the braking-power actual valueachieved by the main brake arrangement and, in the event of adifferential value of braking setpoint—braking actual value >0,activates the emergency brake device so that the differential valuecorresponds approximately to 0, the maximum total braking powerpreferably being ≦130% of the braking-power setpoint. In this especiallypreferred embodiment, if the braking power achieved with the main brakearrangement decreases below the setpoint, the emergency brakearrangement is activated via the control device for producing theadditional braking power required. Limiting the total braking power to amaximum of 130% of the setpoint avoids a situation in which forcesexerted on the components of the drawworks or on other components byinitiating the braking power reach values above the breaking loads ofthese components, thereby avoiding the risk of damage due to theinitiation of excessive braking power.

In a further embodiment of the drawworks according to the invention, theemergency braking arrangement is formed by a feeding device for thecontrolled or regulated lowering, holding or withdrawal of the load, tobe precise by virtue of the fact that the lowering device has a capacitysuitable for braking and holding the maximum hoisting capacity of thedrawworks.

The feeding device preferably comprises an electrically, hydraulicallyor pneumatically driven motor, which also serves to apply the emergencybraking power. Furthermore, if the feeding device comprises a gearbox,to which the motor is coupled, the motor can be coupled to the gearboxvia an additional gear shaft. However, it is likewise possible to couplethe motor to the input shaft of the gearbox for a main drive motor forthe drawworks.

Exemplary embodiments of the invention are shown in the drawing, inwhich:

FIG. 1 shows a first embodiment of a drawworks according to theinvention in a plan view;

FIG. 2 shows a hydraulic plan which shows one possibility for thehydraulic design and activation of the embodiment according to FIG. 1;

FIG. 3 shows a further embodiment of a drawworks according to theinvention in an illustration corresponding to FIG. 1;

FIG. 4 shows a hydraulic plan which shows one possibility for the designand activation of the exemplary embodiment according to FIG. 3;

FIG. 5 shows a cutaway side view of the left-hand region according toFIGS. 1 and 3 of a further embodiment of a drawworks according to theinvention, and

FIG. 6 shows a further embodiment of a drawworks according to theinvention in a view corresponding to FIG. 5.

The drawworks designated overall by 100 in FIG. 1 comprises a frame 1,on which the components of the drawworks are mounted. For withdrawingand lowering and also for holding a load, in particular a drillingimplement or the like, the drawworks 100 comprises a drum 2 which isfastened to a drum shaft 3 in a rotationally fixed manner and the axis Sof which runs parallel to the longitudinal sides 4 of the frame 1. It ismounted in bearing blocks 5, 6 which are arranged beyond the two endfaces 7, 8 of the drum 2.

A brake disk 9 is arranged in a rotationally fixed manner on that regionof the drum shaft 3 which is located on the right of the drum 2 in FIG.1, this brake disk 9 being part of a brake arrangement which isdesignated overall by 10 and furthermore comprises two brake caliperarrangements 11, 12 offset by 180° in the direction of rotation of theaxis S. A further brake caliper arrangement is concealed by the drumshaft 3 and is thus arranged in such a way that it cannot be seen inFIG. 1. By means of the brake arrangement 10, the drum 2 can be brakedin its rotary speed or even completely stopped during the unwindingoperation of a flexible draw means (not shown in the drawing).

To assist the brake arrangement 10 during the braking of an unwindingoperation, an eddy-current brake 13 connected to the drum shaft 3 isprovided on the other side of the brake arrangement 10 as viewed fromthe drum 2.

The drive unit 14 of the drawworks 100 for driving the drum 2 isarranged on the left-hand side of the drum 2 according to FIG. 1. In theexemplary embodiment shown, it comprises three electric drive motors 15,16, 17, of which the two shown at the top are coupled to one another viaa transmission unit 18.

On the output side, the drive motors 15, 16 on the one hand and 17 onthe other hand are operatively connected to gearboxes 19, 20 which arecoupled on the output side to a summation gear 21 which transmits thedrive moment provided by the drive motors 15, 16, 17 to the drum shaft3.

In the drawworks 100, the brake caliper arrangements 11, 12 areconfigured in the manner which can be seen schematically from FIG. 2.They each comprises spring arrangements 22, 23 which press brake shoes(not shown in the drawing) against the brake disk 9. To reduce thebraking force thus exerted on the brake shoes until the brake iscompletely released, hydraulically acting devices 24, 25 are providedwhich are designed in such a way that an admission of pressure leads tothe contraction of the respectively associated spring arrangement 22,23.

Furthermore, each spring arrangement comprises a further device 26, 27which can be actuated hydraulically and with which the spring preloadingcan be increased, which, during actuation, leads to the increase in thebraking force with which the respective brake shoe is pressed againstthe brake disk and thus leads to an increase in the braking power. Tothis end, in the exemplary embodiment shown in FIG. 2, the seat 28, 29absorbing the reaction force of the respective spring arrangement 22, 23is displaced toward the brake disk 9.

The emergency brake device formed by the measures described above isactuated by an emergency switch 30 which can be actuated manually andvia which electromagnetically actuated hydraulic valves 31, 32 areactivated, which upon actuation direct hydraulic fluid from a pressurereservoir 33 via lines 34 to the devices 26, 27.

The configuration described with reference to FIG. 2 of the brakecaliper arrangement may be realized in one brake caliper arrangement orin a plurality of brake caliper arrangements of the brake arrangement.

The further exemplary embodiment, shown in FIG. 3, of a drawworksaccording to the invention, which is designated overall by 200,corresponds in its construction and functioning in essential parts tothe drawworks 100 according to FIG. 1. Accordingly, those components ofthe drawworks 200 which correspond to those of the drawworks 100 areprovided with reference numerals increased by 100. In order to avoidrepetitions, reference may be made in this respect to the abovedescription. Only the differences between the drawworks 200 and thedrawworks 100 are to be explained below.

In the drawworks 200, the shafts of the drive motors 116, 117 areconnected to disk brake arrangements 35, 36, with which the respectivelyassociated shaft can be braked. The disk brake arrangements 35, 36together form an emergency brake device for producing an additionalbraking force.

The disk brake arrangements 35, 36 are actuated in the manner which canbe seen from FIG. 4 via an emergency switch 130 which can be actuatedmanually and via which an electromagnetically actuated hydraulic valve131 is activated, which upon actuation draws off hydraulic fluid fromthe brake calipers 37, 38 via lines 134 to a tank. The brake caliperarrangements 37, 38 of the brake disk arrangements close elastically ina manner corresponding to the brake calipers 111, 112.

In the further exemplary embodiment shown in a cutaway view in FIG. 5,the drawworks is equipped with a feeding device 40 which serves toslowly lower a load by means of the drawworks, for example a drillingdevice at feed rate. To this end, at least one of the gearboxes 19, 26,119, 120 (by way of example reference is only to be made below to thegearbox 20) is provided with an additional input shaft 41 which can becoupled to the main gear shaft (not shown in the drawing). An additionaldrive motor 42 acts on the input shaft 41 via a miter gear 43. Theentire feeding device 40 is dimensioned in such a way that the maximumpermissible hoisting load for the drawworks can be applied by it. It maytherefore be used as an emergency brake device for the case where thebraking power of the brake arrangement of the drawworks diminishes andthere is a risk of uncontrolled lowering of a load. To this end, thedrive motor 42 is designed as an alternating-current motor which isoperated via a frequency converter. To further increase the safety, twoelectric motors may also be provided instead of the one drive motor 42.

The exemplary embodiment of a drawworks shown in FIG. 6 in a cutawayview corresponds in its function to that according to FIG. 5. Here,however, the feeding device (designated overall here by 140) is notformed by a unit connected to the gearbox 20, but rather the drive motor142 is connected via a coupling arrangement 144 to the shaft of thedrive motor 17 on the side opposite the gearbox 20. The drive motor 142may again be replaced by a plurality of motors.

List of Designations

-   1, 101 Frame-   2, 102 Drum-   3, 103 Drum shaft-   4, 104 Longitudinal side-   5, 105 Bearing block-   6, 106 Bearing block-   7, 107 End face-   8, 108 End face-   9, 109 Brake disk-   10, 110 Brake arrangement-   11, 111 Brake caliper arrangement-   12, 112 Brake caliper arrangement-   13, 113 Eddy-current brake-   14, 114 Drive unit-   15, 115 Drive motors-   16, 116 Drive motors-   17, 117 Drive motors-   18, 118 Transmission unit-   19, 119 Gearbox-   20, 120 Gearbox-   21, 121 Summation gear-   22. Spring arrangement-   23 Spring arrangement-   24 Device-   25 Device-   26 Device-   27 Device-   28 Seat-   29 Seat-   30 Emergency switch-   31 Valve-   32 Valve-   33 Pressure reservoir-   34 Lines-   35 Disk brake arrangement-   36 Disk brake arrangement-   37 Brake caliper arrangement-   38 Brake caliper arrangement-   40 Feeding device-   41 Input shaft-   42 Drive motor-   43 Miter gear-   100 Drawworks-   S Axis-   200 Drawworks-   140 Feeding device-   142 Drive motor-   144 Coupling

1. A drawworks for lowering and withdrawing a load, having at least one brake arrangement for braking and holding the load, and an emergency brake arrangement provided for producing an additional braking force, wherein the emergency brake arrangement comprises an additional brake device which can be engaged alternatively to the brake arrangement, wherein a control device is provided which compares a respective braking-power setpoint with a parameter characteristic of a braking-power actual value achieved by the brake arrangement and, in the event of a differential value of braking setpoint braking actual value>0, activates the emergency brake device so that the differential value corresponds approximately to 0, the maximum total braking power preferably being ≦130% of the braking power setpoint.
 2. The drawworks as claimed in claim 1, wherein the brake arrangement has at least one brake shoe acting on a rotary part and a device for applying a braking force to the at least one brake shoe, the emergency brake arrangement being designed in such a way that an additional device for optionally exerting an additional braking force on the rotary part is provided.
 3. The drawworks as claimed in claim 2, wherein the device for applying a braking force to the at least one brake shoe comprises a spring arrangement applying the braking force to the at least one brake shoe.
 4. The drawworks as claimed in claim 3, wherein the device comprises an arrangement which acts in the opposite direction to the spring arrangement and is intended for controlling the braking force exerted on the brake shoe.
 5. The drawworks as claimed in claim 4, wherein the additional device comprises an arrangement for displacing a seat absorbing the reaction forces of the spring arrangement.
 6. The drawworks as claimed in claim 5, wherein the additional brake device is a hydraulically actuated device.
 7. The drawworks as claimed in claim 1, wherein the brake arrangement and emergency brake arrangement are designed in such a way that in each case at least one hundred percent of the maximum braking power required can be achieved.
 8. The drawworks as claimed in claim 1, wherein the construction of the emergency brake arrangement at least essentially the same as that of the brake arrangement.
 9. The drawworks as claimed in claim 1, having at least one gearbox coupled on the input side to a drive motor and interacting on the output side with a summation gear, wherein the emergency brake arrangement is arranged on at least one of an input side and an output side of at least one of the gearbox and the summation gear.
 10. The drawworks as claimed in claim 1, wherein the emergency braking arrangement is formed by a feeding device for the controlled or regulated lowering, holding or withdrawal of the load, this feeding device being suitably designed for braking and holding the maximum hoisting capacity of the drawworks.
 11. The drawworks as claimed in claim 10, wherein the feeding device comprises an electrically, hydraulically or pneumatically driven motor.
 12. The drawworks as claimed in claim 11, wherein the feeding device comprises a gearbox, to which the motor is coupled.
 13. The drawworks as claimed in claim 12, wherein the motor can be coupled to the gearbox via an additional gear shaft.
 14. The drawworks as claimed in claim 12, wherein the motor can be coupled to an input shaft of the gearbox for a main drive motor for the drawworks. 